1. Field of the Invention
The present invention relates to a method of and apparatus for forming, by extrusion, a weather strip for an automobile, particularly, a weather strip having a lip in which the width thereof varies according to the longitudinal position of the weather strip.
2. Description of Related Art
Weather strips have been installed on a phripheral edge of an opening of an automobile body in order to provide a seal between the edge and a mating member, such as a door. A conventional weather strip is shown in FIG. 1. In general, weather strips 21 are formed by well-known extrusion processes in an elongated form and have a cross-sectional shape such as that shown in FIG. 1. More specifically, the weather strip 21 comprises a trim portion 22 having a U-shaped cross-section adapted to be secured to the vehicle body and a lip 23 which extends from the trim portion 22 to the outer side of the vehicle body (rightward in FIG. 1) so as to cover a joint portion of the body thereby improving the appearance of the automobile. The lip 23 has a thickened end portion 23a which faces inwardly of the body (downwardly as viewed in FIG. 1). When the weather strip 21 is installed on the body, the thickened end portion 23a of the lip 23 is in contact with the body.
The configuration of the portion of the body where the weather strip is to be mounted varies according to position. Thus, recently, a demand has arose for a weather strip which enables change in the width W of the lip 23 according to its position with respect to the body. A technique has been proposed, for example in Japanese Unexamined Patent Publication No. 2-24094, to cope with the above-mentioned demand.
This technique employs a roller cutter having upper and lower cutter discs arranged in a pair so as to cut a part of an unvulcanized weather strip immediately after extrusion, thus enabling free change in the width W of the lip 23.
According to this technique, the lip width W is changed simply by severing the end of the weather strip. This means that the thickened end portion 23a of the lip 23 is cut, so that a substantial portion of the thickened end portion 23a is undesirably removed when the width W is to be largely reduced, as illustrated by phantom line in FIG. 2. In such a case, the weather strip has a portion where the width of the thickened end portion 23a is extremely small, with the result that the lip 23 fails to perform the expected function. Furthermore, the cut face of the thickened end portion 23 presents a vertical wall, which impairs overall appearance thereof.
The present invention is provided in order to resolve the above-mentioned problems.
Accordingly, it is a primary object of the present invention to provide a method of, and an apparatus for, forming, through extrusion, a weather strip having a lip which varies in width according to a longitudinal position and which is provided with a thickened end portion, wherein the cross-sectional shape of the thickened end portion is maintained constant regardless of a longitudinal position thereof so as to ensure functioning of the lip while preventing degradation of appearance of the thickened end portion.